Plants are composed in large part of lignocellulosic material and smaller amounts of lipophilic materials (often referred to as “extractives”) and minerals (i.e. ash).
The lignocellulosic material includes lignin, cellulose and hemicellulose.
Cellulose and hemicellulose are each polymeric saccharides (i.e. polysaccharides) of monomeric saccharides (i.e. monosaccharides). Although cellulose and hemicellulose are carbohydrates in a strict chemical sense, the bond types used to connect the monomeric saccharides, and/or the specific monosaccharides in the polymer, make them less physiologically available than other polymeric carbohydrates such as amylan (starch).
Cellulose is rich in six-carbon sugars (hexoses), such as glucose, mannose and galactose. Hemicellulose includes a significant amount of five-carbon sugars (pentoses), such as xylose and arabinose.
Some of these monosaccharides form a large fraction of the total saccharides (e.g. glucose) in the lignocellulosic material, while others are present in relatively low amounts.
Lignocellulosic material is available in a wide variety of forms. In many cases lignocellulosic material is a by-product or waste product. For example, corn stover is a by-product of the corn industry. Alternatively or additionally, the bagasse remaining after initial extraction of sucrose from sugar cane is primarily lignocellulosic. When lignocellulosic material is the by-product, it is often present in a greater quantity by weight than the primary product, as in the case of corn stover and sugar cane bagasse.
In other cases, the primary product is lignocellulosic (e.g. wood produced from timber).